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Liu L, Qu J, Hu Q, Xu J, Liu E, Li Z. Selective uneven enrichment of soil organic carbon among different-sized sediments under a rain-induced overland flow: 13C stable isotope evidence. CHEMOSPHERE 2024; 350:141112. [PMID: 38176587 DOI: 10.1016/j.chemosphere.2024.141112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 12/30/2023] [Accepted: 01/02/2024] [Indexed: 01/06/2024]
Abstract
Soil organic carbon (SOC) enrichment varies among sediments of different sizes during rain-induced overland flow erosion. This selective transport of SOC is complex in conjunction with the exposure of labile and stable organic carbon (OC), accompanied by heterogeneous aggregate disintegration under raindrop effects. Utilizing the variations in δ13C values of SOC fractions, we traced this selective transport, linking it to aggregate-wrapped SOC changes during erosion. A modified soil pan facilitated the simultaneous monitoring of splash and sheet erosion via artificially simulated rainfall, with control over the intensity and slope. Aggregate composition, SOC distribution, and δ13C values in the erosion samples were analyzed. The results indicated that distinct sorting existed within the aggregate fragments. Along with SOC variation among different sediment sizes, the proportions of clay and fine silt within sediment aggregates increased as a function of slope and rainfall intensity, whereas particulate OC within aggregates decreased. The SOC enrichment ratios (ERocs) and δ13C values in splash-eroded sediments were positively correlated with those in sheet-eroded sediments. The ERocs in splash-eroded sediments were lower than those in sheet-eroded sediments, but δ13C values were the opposite. Moreover, δ13C values of SOC enriched in sediment particles of all sizes from aggregate stripping were lower than those of the original soil. This indicates that raindrop hits promote heavy C loss during sheet erosion, which is different for mineral-associated and particulate OC. As the slope and rainfall intensity increased, δ13C values for all sediment sizes decreased over the course of erosion. Interestingly, the highest δ13C values were observed under a rainfall intensity of 60 mm h-1, whereas the highest SOC concentrations were noted on a 5° slope. These observations suggest divergent mechanisms affect δ13C values and SOC concentrations in eroded sediments. All these results verified that selective sorting existed for the light SOC fraction. Finally, the internal selective transport of one SOC fraction may explain the enhanced mineralization and reaggregation capacity of the deposited sediments.
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Affiliation(s)
- Lin Liu
- College of Geography and Environment, Shandong Normal University, Jinan, 250014, PR China.
| | - Jiuqi Qu
- College of Geography and Environment, Shandong Normal University, Jinan, 250014, PR China
| | - Qianping Hu
- College of Geography and Environment, Shandong Normal University, Jinan, 250014, PR China
| | - Jinling Xu
- College of Geography and Environment, Shandong Normal University, Jinan, 250014, PR China.
| | - Enfeng Liu
- College of Geography and Environment, Shandong Normal University, Jinan, 250014, PR China
| | - Zijun Li
- College of Geography and Environment, Shandong Normal University, Jinan, 250014, PR China.
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Zhang D, Li J, Wu J, Cheng X. Soil CO 2 and CH 4 emissions and their carbon isotopic signatures linked to saturated and drained states of the Three Gorges Reservoir of China. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 293:118599. [PMID: 34848288 DOI: 10.1016/j.envpol.2021.118599] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 11/01/2021] [Accepted: 11/25/2021] [Indexed: 06/13/2023]
Abstract
Human activities such as dams disturb the structure and function of wetlands, triggering large soil CO2 and CH4 emissions. However, controls over field CO2 and CH4 emissions and their carbon isotopic signatures in reservoir wetlands are not yet fully understood. We investigated in situ CO2 and CH4 emissions, the δ13C values of CO2 and CH4, and associated environments in the saturated and drained states under four elevations (i.e., the water column, <147 m, permanent inundation area without plants; the low, 145-160 m, frequently flooded area with revegetation; the high, 160-175 m, rarely flooded area with revegetation; and the upland area as the control, >175 m, nonflooded area with original plants) in the Three Gorges Reservoir area. The CO2 emissions was significantly higher in high elevation, and they also significantly differed between the saturated and drained states. In contrast, the CH4 emissions on average (41.97 μg CH4 m-2 h-1) were higher at high elevations than at low elevations (22.73 μg CH4 m-2 h-1) during the whole observation period. CH4 emissions decreased by 90% at low elevations and increased by 153% at high elevations from the saturated to drained states. The δ13C of CH4 was more enriched at high elevations than in the low and upland areas, with a more depleted level under the saturated state than under the drained state. We found that soil CO2 and CH4 emissions were closely related to soil substrate quality (e.g., C: N ratio) and enzyme activities, whereas the δ13C values of CO2 and CH4 were primarily associated with root respiration and methanogenic bacteria, respectively. Specifically, the effects of the saturated and drained states on soil CO2 and CH4 emissions were stronger than the effect of reservoir elevation, thereby providing an important basis for assessing carbon neutrality in response to anthropogenic activities.
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Affiliation(s)
- Dandan Zhang
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China
| | - Jinsheng Li
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China
| | - Junjun Wu
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences (CAS), Wuhan 430074, PR China
| | - Xiaoli Cheng
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China.
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Zheng J, Arif M, Zhang S, Yuan Z, Zhang L, Li J, Ding D, Li C. Dam inundation simplifies the plant community composition. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 801:149827. [PMID: 34467924 DOI: 10.1016/j.scitotenv.2021.149827] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/17/2021] [Accepted: 08/18/2021] [Indexed: 05/20/2023]
Abstract
The construction of dams has caused riparian habitat degradation and ecosystem service loss globally. It is critical to assess the response of riparian plant communities to inundation gradients for their conservation. Recent evidence suggests that plant community assemblages are governed by flooding stress, soil nutrient availability, climate (environmental filtering) and dispersal, speciation, local extinction (dispersal filtering), but it remains unclear which dominates the riparian ecosystem regulated by a dam. Thus, this article aims to elucidate the relative importance of environmental and dispersal filtering to variations in plant communities to understand community assembly mechanisms in riparian ecosystems. Here we used plant community data related to four elevations in the riparian zone of the Three Gorges Dam Reservoir in China to show that species richness and diversity, community height, and the cover of total, annual, and exotic plant categories decreased, while the cover of perennial and native plant groups increased under higher flooding stress. Community composition varied substantially with elevation, and species composition tended to converge with increased inundation, characterized by flood-tolerant species. The community composition underwent stronger environmental filtering at low elevations and stronger dispersal filtering at high elevations, with stronger environmental filtering across riparian ecosystems. Therefore, we conclude that dam inundation drives community assemblages of riparian plants by the combined effects of environmental and dispersal filtering. Still, their relative contribution varies between elevations, and environmental filtering is more important in shaping community assembly. This study is the first to confirm that plant community assembly in the dam-regulated riparian area is determined by both niche-based and stochastic processes. Thus, we highlighted the importance of considering inundation intensity, propagule sources, and river connectivity when implementing restoration projects.
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Affiliation(s)
- Jie Zheng
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
| | - Muhammad Arif
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
| | - Songlin Zhang
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
| | - Zhongxun Yuan
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
| | - Limiao Zhang
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
| | - Jiajia Li
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
| | - Dongdong Ding
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
| | - Changxiao Li
- Key Laboratory of Eco-environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, College of Life Sciences, Southwest University, Chongqing 400715, China.
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Chen Z, Chen X, Wang C, Li C. Foliar Cellulose and Lignin Degradation of Two Dominant Tree Species in a Riparian Zone of the Three Gorges Dam Reservoir, China. FRONTIERS IN PLANT SCIENCE 2020; 11:569871. [PMID: 33424875 PMCID: PMC7793854 DOI: 10.3389/fpls.2020.569871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 11/11/2020] [Indexed: 05/03/2023]
Abstract
The riparian zone can affect the degradation of foliar cellulose and lignin by changing the hydrological gradient of the foliage decomposition environment. However, their degradation dynamics during the process of foliage decomposition remain unclear in mixed plantation forests in a riparian zone. Herein, we explored degradation of cellulose and lignin for two dominant riparian species, bald cypress [Taxodium distichum (L.) Rich.] and Chinese willow (Salix matsudana Koidz.), and a combined treatment with equal proportions of foliar mass of these species, involving three water treatments [no submergence (CK), shallow submergence (SS), and deep submergence (DS)] in a riparian zone of the Three Gorges Dam Reservoir (TGDR), China. Throughout an entire year's incubation, the degradation of cellulose and lignin was 55.57-97.76% and 79.87-93.82%, respectively. In the early stage of decomposition (i.e., the first 30 days), cellulose and lignin were rapidly degraded, and the mass loss of cellulose and lignin in water environments (SS and DS) was greater than that in a non-flooded environment (CK) regardless of the foliage type. The degradation of cellulose and lignin was mainly related to the quality of the leaf litter (as indicated by the concentrations of cellulose and lignin, and the contents of C, N, and P), decomposition period, and local environmental factors (temperature, water gradients, and dissolved oxygen). Our results will provide a clear insight into the material cycling process in a riparian zone of the TGDR and similar ecosystems in other regions.
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Affiliation(s)
- Zhangting Chen
- Key Laboratory of Eco-Environments in the Three Gorges Reservoir Region (Ministry of Education), State Cultivation Base of Eco-agriculture for Southwest Mountainous Land, College of Life Sciences, Southwest University, Chongqing, China
- School of Tourism Management, Guilin Tourism University, Guilin, China
| | - Xuemei Chen
- Key Laboratory of Eco-Environments in the Three Gorges Reservoir Region (Ministry of Education), State Cultivation Base of Eco-agriculture for Southwest Mountainous Land, College of Life Sciences, Southwest University, Chongqing, China
| | | | - Changxiao Li
- Key Laboratory of Eco-Environments in the Three Gorges Reservoir Region (Ministry of Education), State Cultivation Base of Eco-agriculture for Southwest Mountainous Land, College of Life Sciences, Southwest University, Chongqing, China
- *Correspondence: Changxiao Li,
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